Analgesia has historically been achieved in the central nervous system by opiates and analogs which are addictive, and peripherally by cyclooxygenase inhibitors that have gastric side effects. Substance P antagonists induce analgesia both centrally and peripherally. In addition, substance P antagonists are inhibitory of neurogenic inflammation.
The neuropeptide receptors for substance P (neurokinin-1; NK-1) are widely distributed throughout the mammalian nervous system (especially brain and spinal ganglia), the circulatory system and peripheral tissues (especially the duodenum and jejunum) and are involved in regulating a number of diverse biological processes. This includes sensory perception of olfaction, vision, audition and pain, movement control, gastric motility, vasodilation, salivation, and micturition (B. Pernow, Pharmacol, Rev., 1983, 35, 85-141). The NK1 and NK2 receptor subtypes are implicated in synaptic transmission (Laneuville et al., Life Sci., 42:1295-1305 (1988)).
The receptor for substance P is a member of the superfamily of G protein-coupled receptors. This superfamily is an extremely diverse group of receptors in terms of activating ligands and biological functions. In addition to the tachykinin receptors, this receptor superfamily includes the opsins, the adrenergic receptors, the muscarinic receptors, the dopamine receptors, the serotonin receptors, a thyroid-stimulating hormone receptor, a luteinizing hormone-choriogonadotropic hormone receptor, the product of the oncogene ras, the yeast mating factor receptors, a Dictyostelium cAMP receptor, and receptors for other hormones and neurotransmitters (see A. D. Hershey, et al., J. Biol. Chem., 1991, 226, 4366-4373).
Substance P (also called "SP" herein) is a naturally occurring undecapeptide belonging to the tachykinin family of peptides, the latter being so-named because of their prompt contractile action on extravascular smooth muscle tissue. The tachykinins are distinguished by a conserved carboxyl-terminal sequence Phe-X-Gly-Leu-Met-NH.sub.2. In addition to SP the known mammalian tachykinins include neurokinin A and neurokinin B. The current nonmenclature designates the receptors for SP, neurokinin A, and neurokinin B as NK-1, NK-2, and NK-3, respectively.
More specifically, substance P is a pharmacologically-active neuropeptide that is produced in mammals and possesses a characteristic amino acid sequence that is illustrated below:
Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH.sub.2 (Chang et al., Nature New Biol. 232, 86 (1971); D. F. Veber et al., U.S. Pat. No. 4,680,283).
Neurokinin A possesses the following amino acid sequence:
His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH.sub.2.
Neurokinin B possesses the following amino acid sequence:
Asp-Met-His-Asp-Phe-Phe-Val-Gly-Leu-Met-NH.sub.2.
Substance P acts as a vasodilator, a depressant, stimulates salivation and produces increased capillary permeability. It is also capable of producing both analgesia and hyperalgesia in animals, depending on dose and pain responsiveness of the animal (see R. C. A. Frederickson et al., Science., 199, 1359 (1978); P. Oehme et al., (Science, 208,305 (1980)) and plays a role in sensory transmission and pain perception (T. M. Jessell, Advan. Biochem. Psychopharmacol. 28, 189 (1981)). For-example, substance P is believed inter alia to be involved in the neurotransmission of pain sensations [Otsuka et al, "Role of Substance P as a Sensory Transmitter in Spinal Cord and Sympathetic Ganglia" in 1982 Substance P in the Nervous System, Ciba Foundation Symposium 91, 13-34 (published by Pitman) and Otsuka and Yanagisawa, "Does Substance P Act as a Pain Transmitter? " TIPS (Dec. 1987) 8 506-510]. In particular, substance P has been shown to be involved in the transmission of pain in migraine (see B. E. B. Sandberg et al., Journal of Medicinal Chemistry, 25, 1009 (1982)), and in arthritis (Levine et al. Science, (1984) 226 547-549). These peptides-have also been implicated in gastrointestinal (GI) disorders and diseases of the GI tract, such as inflammatory bowel disease, ulcerative colitis and Crohn's disease, etc. (see Mantyh et al., Neuroscience, 25 (3), 817-37 (1988) and D. Regoli in "Trends in Cluster Headache" Ed. F. Sicuteri et al., Elsevier Scientific Publishers, Amsterdam, 1987, pp. 85-95).
It is also hypothesized that there is a neurogenic mechanism for arthritis in which substance P may play a role (Kidd et al., "A Neurogenic Mechanism for Symmetric Arthritis" in The Lancet, 11 November 1989 and Gronblad et al., "Neuropeptides in Synovium of Patients with Rheumatoid Arthritis and Osteoarthritis" in J. Rheumatol. (1988) 15(12) 1807-10). Therefore, substance P is believed to be involved in the inflammatory response in diseases such as rheumatoid arthritis and osteoarthritis (O--Byrne etal., in Arthritis and Rheumatism (1990) 33 1023-8). Other disease areas where tachykinin antagonists are believed to be useful are allergic conditions (Hamelet et al., Can. J. Pharmacol. Physiol. (1988) 66 1361-7), immunoregulation (Lotz et al., Science (1988) 241 1218-21, Kimball et al., J. Immunol. (1988) 141 (10) 3564-9 and A. Perianin, et al., Biochem. Biophys. Res. Commun. 161, 520 (1989)) vasodilation, bronchospasm, reflex or neuronal control of the viscera (Mantyh et al., PNAS (1988) 3235-9) and, possibly by arresting or slowing .beta.-amyloid-mediated neurodegenerative changes (Yankner et al., Science, (1990) 25Q, 279-82) in senile dementia of the Alzheimer type, Alzheimer's disease and Downs Syndrome.
Substance P may also play a role in demyelinating diseases such as multiple sclerosis and amyotrophic lateral sclerosis [J. Luber-Narod et. al., poster to be presented at C.I.N.P. XVIIIth Congress, 28th June-2nd July, 1992, in press], and in disorders of bladder function such as bladder detrusor hyper-reflexia (Lancet, 16th May, 1992, 1239). Antagonists selective for the substance P and/or the neurokinin A receptor may be useful in the treatment of asthmatic disease (Frossard et al., Life Sci., 49, 1941-1953 (1991); Advenier, et al., Biochem. Biophys. Res. Comm., ! 84(3), 1418-1424 (1992)).
It has furthermore been suggested that tachykinins have utility in the following disorders: depression; dysthymic disorders; chronic obstructive airways disease; hypersensitivity disorders such as poison ivy; vasospastic diseases such as angina and Reynauld's disease; fibrosing and collagen diseases such as scleroderma and eosinophillic fascioliasis; reflex sympathetic dystrophy such as shoulder/hand syndrome; addiction disorders such as alcoholism; stress related somatic disorders; neuropathy; neuralgia; disorders related to immune enhancement or suppression such as systemic lupus erythmatosis (EPO Publication No. 0,436,334); ophthalmic diseases such as conjunctivitis, vernal conjunctivitis, and the like; and cutaneous diseases such as contact dermatitis, atropic dermatitis, urticaria, and other eczematoid dermatitis (EPO Publication No. 0,394,989).
In the recent past, some attempts have been made to provide peptide-like substances that are antagonists for substance P and other tachykinin peptides in order to more effectively treat the various disorders and diseases listed above. See for example European patent applications (EPO Publication Nos. 0,347,802, 0,401,177 and 0,412,452) which disclose various peptides as neurokinin A antagonists. Similarly, EPO Publication No. 0,336,230 discloses heptapeptides which are substance P antagonists useful in the treatment of asthma. Merck U.S. Pat. No. 4,680,283 also discloses peptidal analogs of substance P.
Certain inhibitors of tachykinins have been described in U.S. Pat. No. 4,501,733, by replacing residues in substance P sequence by Trp residues.
A further class of tachykinin receptor antagonists, comprising a monomeric or dimeric hexa- or heptapeptide unit in linear or cyclic form, is described in GB-A-2216529.
The peptide-like nature of such substances make them too labile from a metabolic point of view to serve as practical therapeutic agents in the treatment of disease. The non-peptidic antagonists of the present invention, on the other hand, do not possess this drawback, as they are expected to be more stable from a metabolic point of view than the previously-discussed agents.
It is known in the art that baclofen (.beta.-(aminoethyl)-4-chlorobenzenepropanoic acid) in the central nervous system effectively blocks the excitatory activity of substance P, but because in many areas the excitatory responses to other compounds such as acetylcholine and glutamate are inhibited as well, baclofen is not considered a specific substance P antagonist. Pfizer WIPO patent applications (PCT Publication NOS. WO 90/05525 and WO 90/05729) and publications (Science, 251, 435-437 (1991); Science, 251,437-439 (1991)) disclose 2-arylmethyl-3-substituted amino-quinuclidine derivatives which are disclosed as being useful as substance P antagonists for treating gastrointestinal disorders, central nervous system disorders, inflammatory diseases and pain or migraine. A Glaxo European patent application (EPO Publication No. 0,360,390) discloses various spirolactam-substituted amino acids and peptides which are antagonists or agonists of substance P. A Pfizer WIPO patent application (PCT Publication No. WO 92/06079) discloses fused-ring analogs of nitrogen-containing nonaromatic heterocycles as useful for the treatment of diseases mediated by an excess of substance P. A Sanofi publication (Life Sci., 50, PL101-PL106 (1992 )) discloses a 4-phenyl piperidine derivative as an antagonist of the neurokinin A (NK2) receptor.